Burned Hydraulic Oil 1

[uacar]

Friends,

We used mineral oil in the hydraulic unit. Three times changed hydraulic oil.The oil seems burned and smelling like burned. The unit temperature around at 40 degC.Why did it burned in the unit?

Alper

 

[evelrod]

In any oil lubricated/cooled machinery it is quite common for localized temps to be substantially higher than the overall lubricant temp. If your lube is "okay" at 40 and is ending up "burned" then it is probable that at some point the oil has been heated to well beyond it's max temp capacity. Go for a lube that can withstand a higher temp for the short cure and/or fix the part that is overheating the oil.

Rod

 

[boo1]

The four major causes of hydraulic oil deterioration are: Particulate Contamination, Moisture Contamination, Acid Build-up, and Oxidation. Standard hydraulic mineral oils are only designed to handle a maximum of 120 degC. Any greater than this, and the oil will severly breakdown and oxidize.

I would suspect oxidation. Rapid oxidation occurs when hydraulic oil is "cooked" in an overheated situation normally brought about by inadequate cooling or an improperly functioning system. Cooked oil is a dirty brown color and machine parts look "varnished.

The problem is most likely due to thermal stressing of the oil, as opposed to straight oxidation. Improperly functioning system can causing the oil to over heat. Small localized hot spot in a valve or motor cook the oil, but a high temperature would never detected as a rise in bulk oil temperature. Your first indication of a problem is the change in the oil’s color.

Remember to drain and flush the entire system and clean or replace any filter screens. Also you should check with your lube representative or supplier for recommendations and compatibility. Consider changing to a synthetic oil. Did you check the oils Viscosity and PH?

 

[gbednar]

While the machine is in operation and at operating temperature, measure the tempuratue on the valves, cylinders, pumps, ect... You could use a infared camera or one of those non-contact temperature gun that you point at the surface you want to measure. My first thought would be that you may have pressure reducing or relief valve that is set incorrectly and constantly bypassing the extra pressure ( I suppose if you have a variable displacement pump, the pressure may be set to high). Believe me, if this is the case you will heat the oil up considerably. Let me know what you find.

 

[chicopee]

Since somebody mentioned a viscocity test and Ph+ reading
also do a color test but best of all a metal test which will actually tell you the most probable cause of the problem. Any lab that does a metal test will hone in on the problem.

 

[evelrod]

In racing, I run across all sort of problems with oil and lubricants. These folk do an ok job. No affiliation, either.

http://www.titanracinglab.com

Rod

 

[uacar]

Thanks friends,

The unit operating time only 2 years. As a hydraulic oil base on mineral oil.Every two month we analyzed in laboratuvary for viscosity, pH, water, wearing elements,etc...
TAN value (total acidite number)and oil viscosity a little decreased, wearing elements into limits,no water in tank, but Zn (Zinc) value decrease very shortly(This value shows quantity of oil additive).
Why did decreased oil additive quantity?

Otherwise I checked and measured every point with non-contact temperature gun(on the valves, cylinders, pumps, ect...). I measured temperature
not too much(generally 30-40 degC).

 

[evelrod]

Well, perhaps you simply need a better grade of lubricant to start with. Pick one that is less temperature sensitive, or at least more tolerant of high temp. Have you researched the possibility of using a synthetic base lube?

Rod